This patent application hereby incorporates by reference herein in their entirety the following: U.S. Provisional Patent Application No. 61/340,960, filed Mar. 25, 2010, entitled “METHOD AND SYSTEM FOR PROVIDING AUTOMATIC GATE BIAS FOR FIELD EFFECT TRANSISTORS,” U.S. Pat. No. 8,188,794, issued May 29, 2012, and entitled “METHOD AND SYSTEM FOR PROVIDING AUTOMATIC GATE BIAS FOR FIELD EFFECT TRANSISTORS,” and U.S. Utility Patent Application No. 13/481,906, filed May 28, 2012, entitled “METHOD AND SYSTEM FOR PROVIDING AUTOMATIC GATE BIAS SEQUENCING FOR FIELD EFFECT TRANSISTORS.”
In addition, as taught by Lautzenhiser et al., in U.S. Pat. No. 7,936,218 on May 3, 2011, which is incorporated herein by reference, two or more solid-state electronic devices, or at least one solid-state electronic device and at least one other electronic device, are connected in series between positive and negative terminals of a dc source voltage, thereby proportioning the dc source voltage between or among the electronic devices. The solid-state electronic devices may be gallium arsenide field-effect transistors (GaAsFETs) or any other type of solid-state electronic device. All of the dc series-connected electronic devices may use the same current flow, or some current may be bypassed around an electronic device that uses less current than an other current-sharing device. Alternately, two solid-state electronic devices that use less current are connected in dc parallel in a stack with two or more solid-state electronic devices to best utilize, not only the dc source voltage, but also the current required by the power-amplifying FETs. If the solid-state electronic devices are field-effect transistors (FETs), the FETs are stacked like a totem pole with the drain of a top, or upper, FET being operatively connected to a relatively high positive potential, a source terminal of the top FET being connected to a drain terminal of a lower FET, and a source terminal of the lower FET being connected to a lower voltage. An RF power splitter is used to split the RF input two or more ways for the gates of the FETs. In various ones of the embodiments, an RF power combiner is connected to the drain terminals of the FETs to combine the RF outputs. A negative gate-to-source bias for the lower FET controls current flow through all FETs, which in turn controls power amplification. In addition to proportioning a dc source voltage between, or among, a plurality of solid-state amplifying devices in fixed proportions for the purpose of providing dc voltages that are usable by various types of solid-state amplifying devices, the dc source voltage may be variably proportioned between, or among, a plurality of solid-state amplifying devices. The dc source voltage may be variably proportioned for the purpose of variably shifting a phase angle of an RF output, or the dc source voltage may be variably proportioned for the purpose of selectively proportioning, or switching, RF power from one RF output and an antenna to an other RF output and its antenna. A power combiner is used to combine the RF signals after being power amplified by the FETs, in other embodiments, the RF signals are used separately. Separate RF inputs, which may be at different frequencies, different levels, and different modulation types, are separately amplified, and then combined to produce both RF signals in a single RF output.
The present invention provides an improved high power RF (radio frequency) splitter/combiner that is appropriate for use in a wide range of frequencies and applications, including KHz to GHz, including in the L, S, and C bands. The S band ranges from 2 to 4 GHz and is part of the microwave band of the electromagnetic spectrum used in weather radar, surface ship radar, and communications satellites applications. The L band, referred to as the IEEE L band, is a portion of the microwave band of the electromagnetic spectrum ranging from 1 to 2 GHz. The L band is used in communications, digital audio broadcast, satellite communications, telecommunications, military, telemetry as well as other applications. For instance, the Global Positioning System (GPS) utilizes carriers in the L band. Uses for IEEE C-band frequencies, which extend from 4 to 8 GHz, include satellite communications, weather radar, and military applications.
Exemplary uses of the RF splitter-combiner of the present invention are transmission applications, including transmitters, receivers, and power amplifiers. Applications for the invention include two-way private radio communication, broadband amplifiers, cellular infrastructure, test instrumentation, and Class A, AB, Linear amplifiers suitable for OFDM, W-CDMA, EDGE, and CDMA waveforms. Microstrip Splitter-combiners preferably provide minimal insertion loss with high isolation between output ports along with phase and amplitude balance and may be arranged in N, SMA, BNC, TNC and 7/16 DIN connector styles for frequencies from 0.4 to 18.0 GHz for narrow, octave, dual and multi-octave band applications.
Power dividers or splitters are what the name implies—a device to divide a signal into two or more parts. They may also be used as combiners since they are fully bi-directional. The outputs may have an amplitude or phase relationship and will usually cover a specific frequency range. For example, an in-phase divider will have outputs that have a zero degree relationship to each other and have the same amplitude. A 180 degree divider has equal amplitude outputs but they will be 180 degrees apart in phase. Another example is a device having both in-phase and 180 degree outputs. A 90 degree or quadrature divider will have outputs that are 90 degrees apart with the same amplitudes over a specific frequency range. The range is usually limited to a 2:1 maximum ratio. A narrow-band divider will usually cover a specific frequency but can be used over a 10% bandwidth quite well.
In-phase power dividers, such as those available from Emhiser Tele-Tech, Inc. of Belgrade, Mont., are available for 2-way up through 32-way. Impedances are available for both 50 ohm and 75 ohm. Maximum signal level is typically +20 dbm but higher power levels can be handled with special considerations. Dividers able to handle high power preferable will require that any unused inputs/outputs be terminated into a suitable load to properly dissipate the energy outside of the unit. Power dividers can be used in any application that a signal needs to be divided or multiple signals combined. For example, multiple devices that require the same signal input, splitting a signal for feeding many antennas or splitting a signal for use in a feedback system. Typically, combiners are used to integrate multiple signals into one signal stream, combining the outputs of several amplifiers before feeding the signal to an antennae or, as in the case of a cell phone system, combining many phone calls into one transmitted signal.
A widely used design is the Wilkinson Power Divider, which is a specific class of power divider circuit that can achieve isolation between the output ports while maintaining a matched condition on all ports. The Wilkinson design can also be used as a power combiner because it is made up of passive components and hence reciprocal. This circuit is widely used in RF communication systems utilizing multiple channels because its high degree of isolation between the output ports prevents crosstalk between the individual channels.